US2024053136A1PendingUtilityA1
Method of Processing Interferometry Signal, and Associated Interferometer
Est. expiryDec 18, 2040(~14.4 yrs left)· nominal 20-yr term from priority
Inventors:Selene Rodd-Routley
G01J 3/45G01B 9/02061G01B 9/02084G01J 9/02G01B 9/02027G01J 2009/0238G01J 3/453G01J 3/2803G01J 3/0297G01J 3/027
40
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Claims
Abstract
The present invention relates to a method of reducing phase-error signal degradation in a characteristic spectrum produced by a Fourier Transform interferometer, comprising the steps of: (1) Receiving, upon the detector array, a light beam comprised of a plurality of light channels, each of the light channels being received at a corresponding location upon the detector array; (II) Producing, for each corresponding location, a Raw Location-Specific Signal (LSS) from the received light channels; (III) for each Raw LSS, calculating an Off-Axis Path Difference (OxPaDE) scaling function dependent upon a distance and direction of the corresponding location from a target location; (IV) coordinate-transforming each Raw LSS using their corresponding calculated OxPaDE function to produce an Adjusted LSS; (V) averaging each Adjusted LSS to produce a Combined Signal; and (VI) inverse Fourier-Transforming the Combined Signal to produce the characteristic spectrum of the received light beam as a function of wavenumber.
Claims
exact text as granted — not AI-modified1 . A method of reducing phase-error signal degradation in a characteristic spectrum produced by a Fourier-Transform interferometer comprising a collimator and a detector array, the method comprising the steps of:
I. Receiving, upon the detector array, a light beam comprised of a plurality of light channels, each of the plurality of light channels being received at one of a plurality of corresponding locations upon the detector array; II. Producing, for each corresponding location, a Raw Location-Specific Signal (LSS) from the received light channels; III. for each Raw LSS, calculating an Off-Axis Path Difference (OxPaDE) scaling function dependent upon a distance and direction of the corresponding location from a target location; IV. coordinate-transforming each Raw LSS using their corresponding calculated OxPaDE function to produce, from each Raw LSS, a coordinate-transformed LSS; V. combining and averaging each Adjusted LSS to produce a Combined Signal; and VI. inverse Fourier-Transforming the Combined Signal to produce the characteristic spectrum of the received light beam as a function of wavenumber;
wherein the target location is a corresponding location on the detector array at which phase-error noise is substantially zero.
2 . The method of claim 1 , wherein each Raw LSS is a signal intensity function comprising a set of received signal intensity values and corresponding set of induced path length values; and
Step IV comprises, for each Raw LSS, the sub-steps of:
a. applying the OxPaDE Scaling Function to determine an actual path length value for each induced path length value within the set of induced path length values, such that each received signal intensity value subsequently corresponds to an actual path length value;
b. coordinate-transforming the set of received intensity values to determine a set of coordinate-transformed signal intensity values, which comprises a coordinate-transformed signal intensity value for each induced path length value; and
c. generating the Adjusted LSS as a signal intensity function comprising the set of induced path length values and corresponding set of coordinate-transformed signal intensity values.
3 . The method of claim 2 , wherein the OxPaDE Scaling Function is linearly proportional to induced path length.
4 . The method of claim 3 , wherein:
the OxPaDE Scaling Function is a function of an angle of deviation (θ), being an angle between the received light channel and an optical axis extending through the target location; a particular corresponding location, having a particular distance and particular direction from the target location, receives light channels having a particular θ substantially according to each of the particular distance and the particular direction.
5 . The method of claim 4 , wherein:
the OxPaDE Scaling Function is given by the following Equation:
Π
(
L
i
,
γ
x
,
γ
y
)
=
L
i
2
sin
2
θ
and the actual path length value is given by the following equation:
L act =L i +π( L i ,γ x ,γ y )
further wherein:
θ is the angle of deviation in radians;
L i & L act are an induced/actual path length difference in units of length; and
γ x and γ y are x-axis and y-axis direction cosines of θ, the x and y axes being perpendicular to one another and to the optical axis.
6 . The method of claim 5 wherein the plurality of light channels received by the detector array satisfy the Equation 0≤|θ|≤|θ max |; and
when |θ max | is such that sin θ max ≈θ max the OxPaDE Scaling Function is approximated by the following Equation:
Π
(
L
i
,
γ
x
,
γ
y
)
=
L
i
2
sin
2
θ
≈
L
i
2
θ
2
7 . The method of any one of the above claims, wherein the detector array comprises a plurality of detector pixels, each detector pixel being positioned at a separate one of the plurality of corresponding locations; and
the Raw and Adjusted Location-Specific Signals are Raw and Adjusted Single-Pixel Signals, respectively.
8 . The method of claim 7 when dependent upon claim 4 , wherein:
each detector pixel comprises a first pixel edge and a second pixel edge spaced apart by a width; and
the width is such that a change in θ of a signal incident thereupon proximate the first edge, compared to being incident thereupon proximate the second edge, and therefore a change in the OxPaDE Scaling Function, is negligible.
9 . The method of claim 7 , wherein negligible change in the OxPaDE Scaling Function ultimately corresponds to a change in the characteristic spectrum that is lower than a spectral resolution of the detector pixel array.
10 . The method of claim 1 , wherein each Raw LSS is a location-specific received signal intensity function, being received signal intensity as a function of an induced path length variable (L); and
Step IV comprises, for each Raw LSS, the sub-step of modifying the received signal intensity function to be received signal intensity as a function of the induced path length variable plus OxPaDE.
11 . The method of claim 10 , wherein the sub-step of modifying the received signal intensity function comprises modifying the function to comprise the following Equation:
I
L
S
S
(
L
,
θ
)
=
I
0
2
-
∫
All
Wavenumbers
G
(
k
)
cos
(
k
L
+
Π
(
θ
)
)
d
k
further wherein:
I 0 is the idealised signal intensity function; and
π(θ) is the OxPaDE scaling function as a function of the angle of deviation (θ) of a particular light channel.
12 . The method of claim 11 , wherein the angle of deviation is expressed as a function of x- and y-axis direction cosines, the Equation comprises:
I
L
S
S
(
L
,
γ
x
,
γ
y
)
=
I
0
2
-
1
2
∫
-
∞
∞
G
(
k
)
cos
(
k
L
+
Π
(
k
L
,
γ
x
,
γ
y
)
)
d
k
13 . A Fourier-transform spectrometer comprising:
a detector array arranged to receive a light beam comprised of a plurality of light channels, each location producing a Raw Location-Specific (LSS) from the received light channels; a coordinate-transformation means for coordinate-transforming each Raw LSS according to the corresponding location's position within the array, the coordinate-transformation means producing an Adjusted LSS from each Raw LSS; an averaging means for determining a Combined Signal from the Adjusted LSS; and an inversion means for inverse Fourier-transforming the Combined Signal in order to produce a characteristic spectrum of the received light beam as a function of wavenumber.
14 . A processor configured to receive a Raw Location-Specific Signal (LSS) as an input from at least one corresponding location within a detector array and enact the following algorithm:
a. determine location information for the at least one corresponding location; b. calculate an Off-Axis Path Difference (OxPaDE) scaling function using the determined location information; c. adjust the Raw LSS, being a received signal intensity as a function of an induced path length, based upon the calculated OxPaDE scaling function; and d. generate an Adjusted LSS by coordinate-transforming the adjusted Raw LSS signal intensity function at each value of the induced path length.Cited by (0)
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